Department of Biosciences, Swansea University, Swansea SA2 8PP, United Kingdom.
Stream Biofilm and Ecosystem Research Laboratory, Institute of Environmental Engineering, School of Architecture, Civil and Environmental Engineering, Ecole Polytechnique Fédérale de Lausanne, Station 2, 1015 Lausanne, Switzerland.
Water Res. 2018 Aug 1;139:30-37. doi: 10.1016/j.watres.2018.03.060. Epub 2018 Mar 27.
Chaoborus spp. (phantom midge) are prevalent in eutrophic inland waters. In Lake Soppen, Switzerland, C. flavicans larvae diurnally migrate between the methane-rich, oxygen-depleted hypolimnion and sediments, and the methane-poor, oxygen-rich epilimnion. Using a combination of experiments and system modelling, this study demonstrated that the larvae's burrowing activities in and out of the sediment perturbed the sediment and re-introduced sequestered phosphorus into the overlying water at a rate of 0.022 μg P ind d, thereby exacerbating internal nutrient loading in the water column. Fluxes of sediment methane and other reduced solutes enhanced by the larval bioturbation would consume oxygen and sustain the hypoxic/anoxic condition below the thermocline. In addition to increasing diffusive fluxes, migrating larvae also directly transported methane in their gas vesicles from the deep water and release it in the surface water at a rate of 0.99 nmol CH ind d, potentially contributing to methane emission to air. As nutrient pollution and climate warming persist or worsen in the coming decades, proliferation of Chaoborus could intensify this positive feedback loop and delay lake recovery.
水虿（幻影摇蚊）普遍存在于富营养化的内陆水域中。在瑞士的索彭湖，C. flavicans 幼虫在富含甲烷、缺氧的下湖层和沉积物与贫甲烷、富氧的上湖层之间进行日周期性迁移。本研究采用实验和系统建模相结合的方法，证明了幼虫在沉积物中的钻洞活动扰乱了沉积物，并以 0.022μgP ind d 的速率将被隔离的磷重新引入上覆水中，从而加剧了水柱内部的营养负荷。受幼虫生物扰动增强的沉积物甲烷和其他还原溶质的通量会消耗氧气，并维持温跃层以下的缺氧/厌氧条件。除了增加扩散通量外，迁移的幼虫还通过其气囊直接从深水输送甲烷，并以 0.99nmol CH ind d 的速率将其释放到地表水，这可能导致甲烷向大气排放。在未来几十年，随着营养污染和气候变暖的持续或恶化，Chaoborus 的增殖可能会加剧这种正反馈循环，并延迟湖泊恢复。
